To meet the demand for increased air travel, aircraft have become larger with more mass, more engine power, larger wing spans and stronger landing gear. This trend has led to longer (approximately 13,000 ft) and wider (approximately 200 ft) runways for the most recently designed long haul aircraft—categorized as super jumbo jets. Wider runways allow for clearances to aircraft on adjacent runways or taxiways. Longer runways allow for longer takeoff runs and landings without requiring excessive engine sizes but are limited in takeoff velocity by tire specifications. The larger airplanes require upgrades to pavement, taxi lanes and arrival lanes due to much larger weight and turning forces.
The largest airports in the most populated cities of the world face land constraints where additional runways or longer runways require land acquisition or extending land into surrounding waters. Prior methods for extending civil airport capacity include adding additional runways at current airports, adding additional airports in neighboring regions, or some combination. The replacement of Stapleton airport near downtown Denver, Colo. with Denver International Airport to the north east of Denver provides an example of prior airport design and abandonment for more-distant vacant land. Los Angeles International Airport is bordered by the Pacific Ocean to the west, dense housing to the north and south, and mixed-use land to the east. The Federal Aviation Authority in the United States of America has acquired many acres of land to the west between the airport and ocean, and to the north. Plans to expand the airport capacity by moving runways or adding runways to the north have not overcome opposition to noise, pollution, and traffic congestion on roads leading to the airport. Heathrow Airport in London faces similar opposition to expansion.
New York's John F. Kennedy and LaGuardia airports border water and highly populated regions making expansion difficult and expensive. Relocating these airports seems intractable given the size of the public transportation structure that travelers use to access the airports. Even if support transportation was easy to reconfigure, there is no land available in these highly populated areas that would offer improved airport capacity. Expanding these two airports further into adjacent waters offers additional land but at the expense of environmental and waterway concerns. Proposals for a new floating airport in the Thames Estuary for London offers an example of political interest in complete airport relocation.
In these busy airports, runways are managed using time slots available for certain weight class of aircraft. Since all time slots at congested airports are allocated, more airplanes cannot be accommodated, so larger aircraft have been used to increase passenger and freight. Longer aircraft weigh more and produce larger wakes, potentially offsetting increased throughput with longer time slots. The variability of aircraft weight class is one of many factors affecting the dynamics of delays for different levels of utilization. As mentioned above, aircraft of heavier weight classes typically need longer runways, occupy the runway longer, but lift more mass.
New York and London regional studies estimate lost economic activity due to limited airport capacity between $100 B and $150 B over ten years for each of their regions, making the general economic benefit estimate in the order of $10 B to $15 B per year. These estimates are for economic benefits of both increased business activity and serving a growing population but do not account for indirect costs the population might incur.
The economic cost of air pollution on citizens of each city will increase as more jet fuel is used within the confined region of the airport. Newer airplanes bring improved fuel efficiency but provide added cargo capacity and higher thrust engines that burn more fuel on the runway. Cleaner burning engines, while helpful, do not overcome the rate of increasing demand for air travel in these highly dense and growing populations. In New York, new zoning allows constantly taller buildings to accommodate new business and apartments. Yet, the new people filling the taller apartments add to the overall population that must share a single-story runway that cannot build out or up. Recent estimates of economic costs of living with pollution in the Los Angeles region exceed $28 B per year. This is most concentrated to the east of the airport, but also includes pollution from all sources. Strict regulations on car emissions in the Southern California region suggest that a significant share of this cost might come from the Los Angeles International Airport.
In addition to the runway constraints, the largest airports in the most populated cities of the world face airspace constraints from overlapping flight paths from adjacent airports. New York's John F. Kennedy and LaGuardia along with New Jersey's Newark airports serve a large population of New York City and its surrounding areas. Even as the population has increased, fewer airplanes are operating through LaGuardia due to overlapping flight paths for aircraft operating out of Newark or John F. Kennedy. Passengers landing at JFK who need to travel to New Jersey face limited subway capacity and increasing delays due to cancellation of the subway expansion projects. In addition, attempts to push air traffic to airports in New Jersey to the north or south of Newark face limited ground support transportation and would further increase overlapping flight paths, the very reason cited for the need to relocate air traffic in the first place. In Report No. ICAT-2011-4 Febuary 2011, Alexander empirically estimates the capacity of airports from flight path data. However, outside the scope of the thesis are estimates for what the capacity could be within the airspace if limitations of aircraft acceleration power were overcome.
Given the land, runway, and flight path constraints discussed above, there is a need for more efficient systems and methods for effectively increasing airport throughput.